抄録
Humic substances (HS) , which are the naturally occurring heterogeneous mixtures of various macro molecules, are expected to strongly affects the fate and transportation of heavy metals ions by the formation of their complexes. To quantitatively describe such complex formation, it is essential to take into account the effect of heterogeneous composition and polyelectrolyte properties of humic acid (HA) on the complex formation. The aim of this work is to clarify the effect of heterogeneity of HS on the complex formation with calcium ion. The free calcium ion concentration was measured by calcium ion selective electrode. The experimental results shows that the apparent complexation constant decreases with the free calcium ion concentration for the complexation with humic substances, while the complexation constant of PPA is nearly constant. This result indicats that the heterogeneous effect in HS reflects on the dependence of logKapp on the the mental ion concentration.
